1.4.1

The Teleological Argument - Aquinas' Fifth Way

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A Posteriori Arguments: The Teleological Argument

The word teleological comes from the Greek word telos, meaning goal or purpose. The world and things in it seem to move towards certain goals or ends.

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A posteriori arguments

  • Arguments based on observation are called in Latin a posteriori arguments.
  • These have a prominent place in the philosophy of religion.
  • Aquinas’ five ways are all a posteriori as he did not believe an a priori argument (an argument based purely on logic or deduction) for God would be valid.
  • This was a consequence of the epistemology (theory of knowledge) that he had inherited from Aristotle.
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Efficient & final causes

  • Aristotelian-Thomistic scholars (working in the tradition of Aristotle and St. Thomas Aquinas) say that efficient causality is unthinkable without final causality.
    • Efficient causes change things or bring them into existence (e.g. heat is the efficient cause of the melting of ice and phosphorous in a match head is the efficient cause of the flame on a match).
    • Final causes are just the outcome of these causes – the water/the flame. When we talk about telos, we mean these final causes.

The Teleological Argument: Aquinas' Fifth Way

Teleological arguments go all the way back to Plato. Plato proposed that the cosmos is directed by intelligence.

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Aquinas' fifth way

  • Aquinas' fifth way uses the observation that non-intelligent organic life acts in certain ordered, cyclical and purposive ways. For example:
    • Given the right conditions, acorns always grow into oak trees and not wombats.
    • The moon has a regular 29 and a half-day cycle.
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Acting for goals & intelligence

  • The fact that non-intelligent things (like acorns and plankton) always act in certain ways for certain goals implies that they were given those goals by intelligence because only intelligent beings can assign a purpose to things and move that thing towards its purpose.
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Archery example

  • Aquinas gives the example of arrows fired by an archer to hit a target.
    • Without the archer giving the purposive direction, the arrow would remain in the quiver.
  • A simplified version of the argument might say that the order and purpose we see in the universe needs an explanation in terms of a guiding intelligence.
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Aquinas’ fifth way

  • The argument can be put like this:
    • The natural world obeys natural laws.
    • Natural things flourish as they obey these laws.
    • Things without intelligence can’t direct themselves.
    • Therefore, things without intelligence require something with intelligence to direct them to their goals.
    • This is God.

Jump to other topics

1Philosophy of Religion

1.1Ancient Philosophical Influences: Plato

1.2Ancient Philosophical Influences: Aristotle

1.3Ancient Philosophical Influences: Soul, Mind, Body

1.4The Existence of God - Arguments from Observation

1.5The Existence of God - Arguments from Reason

1.6Religious Experience

1.7The Problem of Evil

1.8The Nature & Attributes of God

1.9Religious Language: Negative, Analogical, Symbolic

1.10Religious Language: 20th Century Perspective

2Religion & Ethics

3Developments in Christian Thought

3.1Saint Augustine's Teachings

3.2Death & the Afterlife

3.3Knowledge of God's Existence

3.4The Person of Jesus Christ

3.5Christian Moral Principles

3.6Christian Moral Action

3.7Development - Pluralism & Theology

3.8Development - Pluralism & Society

3.9Gender & Society

3.10Gender & Theology

3.11Challenges

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